The wellness visits are pretty well prescribed. Physicians gather medical and family history, update lists of the patient's prescriptions and conduct lots of screenings. Like the one recalled by Dr. Ishani Ganguli, who works at Brigham and Women’s Hospital in Boston.

"I remember meeting this woman. She was in her late 60s. And I was meeting her for the first time," she said. During the visit, Ganguli discovered the woman in front of her was pre-diabetic. The two hatched a plan.

"What we settled on was that she would start to see our nutritionist," said Ganguli. "We had scheduled another visit to see how things were going."

This is how wellness visits are supposed to work. Making diet and exercise changes to hopefully avoid the expensive care that comes with diabetes is just what Medicare wants to see.

But the new research, headed up by Ganguli, shows just 16 percent of those eligible went to a wellness visit.

One reason could be because lots of people still don’t know about it. Another could be that lots of doctors haven’t set up systems. Ganguli finds visits are more common in some cities than others.

Whatever the problem, it certainly doesn’t help that these appointments may come with surprise bills.

"You’re in for your annual wellness visit, and you say, ‘Oh, right, also I’ve been having this protracted cough,' and they take a look and they write you a prescription," said Casey Schwarz, a lawyer with the Medicare Rights Center.

"That is a diagnostic service that’s not part of the annual wellness visit. And so it’s not covered at zero percent cost-sharing," Schwarz said.

The federal government has already invested heavily in the program, with Medicare paying as much as $170 just for the visit alone. Some Medicare recipients even get $25 just for showing up to one of them. No evidence yet has emerged to show these appointments are helping seniors’ health or saving taxpayer money.

What we know so far is that it’s always easier to talk about the importance of providing preventive care than it is to deliver it.